The agricultural chemical formulator has the difficult task of creating a product that balances bioefficacy, toxicity, cost, shelf life and user friendliness.
Of particular importance to the activity of an agricultural formulation is the ability of an aqueous solution to spread evenly over a surface, the so-called wetting ability, and the effective uptake of the active ingredient by the plant to be treated. For example, in agricultural formulations, efficacy benefits from a good wetting of the plant surface and uptake of the active ingredient.
Adjuvants are added to agricultural formulations to improve activity, thereby reducing the amounts of active ingredients necessary, resulting in lower formulation cost. They generally take the form of surface-active or salt-like compounds and, depending on their mode of action, they are classified as modifiers, actuators, fertilizers and/or pH buffers.
Surfactants are generally regarded as modifiers and/or actuators as they improve wetting properties and uptake of the active ingredients in the agricultural formulation. Additionally, some surfactants improve the solubility of active ingredients in formulations thereby eliminating serious issues such as product separation and/or crystallization.
Anionic, cationic, amphoteric and nonionic surfactants are all known and used in agricultural applications depending on the desired effect. For example, nonionic surfactants are known to be good wetting agents, and are often present in agricultural formulations. Many nonionic surfactants are not soluble enough in solutions with a high amount of electrolytes, such as alkali and/or alkaline complexing agents, salts, and the like and therefore need the presence of a hydrotrope to improve the solubility. A hydrotrope is a compound that solubilises hydrophobic compounds in aqueous solutions. A number of hydrotropes for nonionic surfactants have been described in various publications. Examples of such hydrotropes are ethanol, sodium xylene sulphonate, sodium cumene sulphonate, alkyl glycosides, and phosphated alkoxylated alcohols.
Pesticide formulations are becoming more complex and concentrated, with an increase in active loading, number of actives used in a formulation or the inclusion of adjuvants, such as surfactants. Those changes lead to a reduction in the water used in certain kinds of formulations, such as soluble liquids, leading to solubility issues within the formulation. A specific example is with glufosinate-ammonium. Glufosinate-ammonium is a water soluble, phosphinic acid based herbicide used for broad spectrum weed control. Early uses of the herbicide were for non-selective applications but tolerant crops have been engineered so applications now include food crops. The adjuvant used in combination with glufosinate-ammonium is typically an alcohol ether sulfate which is neutralized to form a sodium salt but the ammonium salt can also be used, and the adjuvant is formulated in-can with the herbicide. The ratio of pesticide to adjuvant can range from 1:1 to 1:5. As the ratio of pesticide to adjuvant moves closer to 1:1, the compatibility of the adjuvant becomes more challenging.
Application culture has changed with farmers. In the past pesticides and fertilizers were typically applied separately, but due to time constraints and fuel costs they are being combined and applied in one tank mixes. The ionic strength of the fertilizer solution leads to incompatibilities due to a reduction in the solubility of the surfactants/adjuvants in the pesticide formulation. One way to modify the solubility properties within a formulation and/or to improve the mixing and dispersion of the formulation into the fertilizer is to incorporate a hydrotrope into the recipe. Examples of typical hydrotropes used would be sodium xylene sulfonate or phosphate esters. Both classes of chemistries have drawbacks; sodium xylene sulfonate is an environmental hazard and phosphates esters, due to its very low pH's, is difficult to be incorporated into the formulation at a level high enough to be effective when diluted into the fertilizer. Additionally, the high acidity of phosphate ester makes it unsuitable for use in formulation containing ether sulfate as adjuvant, since it would result in the hydrolysis of the ether sulfate.
The objective of the present invention is, therefore, to find a new agricultural hydrotrope that is efficient in formulating agricultural compositions, which compositions will remain homogeneous upon dilution, and stable, with improved activity. These and other objects are achieved by the formulations of the present invention.